Food and other items are often packaged in flexible containers of thermoplastic material, such as pre-formed bags with one end open through which the product to be packaged is inserted into the bag, or pouches that are formed of a flat or folded film sealed around the product to be packaged, which are then closed by heat-sealing the open end(s).
Particularly with food products, the flexible container is often made of heat-shrinkable thermoplastic material. In such a case, the product is loaded into the flexible container, then air is removed from the container and the open end of the container is closed by a heat-sealing step. Finally, the sealed and vacuumized package is submitted to heat-treatment so as to get the shrink of the packaging material tightly around the packaged product. The opening of vacuumized and shrunk bags may present a real problem, particularly if no cutting tools are available. Therefore, it is desirable to provide the flexible container with a so-called easy-opening feature, i.e., a feature or a combination of features that would enable the end user to easily open the package by hand.
U.S. Pat. No. 3,516,537 addresses this problem by creating a tab in the skirt of a heat-shrinkable bag extending beyond the factory seal of the bag, by means of a cut at a right angle to the factory seal. To open the package, the tab is gripped with the fingers of one hand and pulled up and across the bottom of the package, while the packaged product is held with the other hand. The entrance edge of the tab, being directed at a right angle to the seal, will tear into and through the factory seal. As the tab is pulled across the package, the package will tear open predominantly following the sealed seam. This solution, however, can only be employed with products that would not be damaged by a certain pressure, such as the pressure exerted by pulling up the tab with one hand while keeping down the product with the other or that specifically illustrated in U.S. Pat. No. 3,516,537.
A similar approach, with similar drawbacks, has been described in U.S. Pat. No. 3,641,732, where a laminated tear tab extending outwardly and substantially perpendicular to the package is formed by the fusion of a suitable portion of the wrapping material.
A different approach has been followed in U.S. Pat. Nos. 3,391,851 and 5,413,412 where a tear tab is sealed over a perforation line on a heat-shrunk container or on a heat-shrinkable bag. The drawbacks of these solutions are related to the risk that the accidental detachment of the adhered tear tab would expose the perforations and, thus, lead to a loss of vacuum within the package.
Still another approach has been described in U.S. Pat. No. 4,958,735. It provides for the adhesion of a thick strip of non shrinkable thermoplastic material adhered to the un-shrunk portion of an otherwise shrunk package, with the thick strip bearing a weakness line dividing it into two manually graspable sections to be used as tear tabs and pulled into the opposite directions to open the package. While this system has certain advantages, for instance there is no need to keep the packaged product from moving while opening the package and there are no risks for the packaged product if the tear tabs detach from the bag, the manufacture of such a package would be complicated and difficult on an industrial scale. Furthermore, the opening of the package will occur through a tear of the shrunk film in the longitudinal direction, effectively destroying the whole container.
There is, therefore, still a need for flexible containers provided with improved easy-opening.